The invention disclosed herein pertains to a multiple position rotary switch.
Rotary switches are used in many applications for switching current values of 1 mA to 25 amperes. Rotary switches of the indicated ratings are frequently used as control and function selectors in major domestic appliances such as dish and clothes washing machines and clothes dryers. The environment in these machines is usually wet, humid and soapy and is, therefore, hostile to electrical devices such as switches, connectors, and so forth. In the case of a rotary switch in such appliance, it is highly desirable for it to be sealed against entry of moisture or other contaminants which might cause a short circuit and/or corrosion that could disable the switch and the entire machine.
In most preexisting rotary switches, the stationary and movable contacts are coated with a non-oxidizing noble metal, silver being most common. Even so, a nonconductive or poorly conductive film may form on the contacts which can increase contact-to-contact resistance, unless the film is fractured when the stationary and movable contacts meet. Rotary switches having low current ratings usually utilize movable contacts that are rather small and have contact tips that are tiny. It is difficult to hold small contacts for applying a silver coating by electroplating, hot dipping or vapor deposition where it is desirable for cost reduction reasons to not coat the main body of the contact with costly noble metal.